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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4c5a317e922fc5ea2276d8c16bda91fd10d974c5c21a07f25e5e4eb6bab3c71' 
  AND token = 'RTQ9J47Qfj+2w1VG0XgcHN2VZ+UqRv2NdtSJ2pUdq7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}