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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68f4ea7e9441612b0776beb76a8cd4a8cd8ae72035984e7342d920a44e5ee552' 
  AND token = '29KZIGf30VTAoxyVl0tVlBhI/k02qa+nukdY5hM/FQg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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