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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4ed39f9f1f3c0f8112d40bdbbe822e5749915d0724aec6a784e06591a3740f3e' 
  AND token = 'Cpg9DVSY1FRW2sJQhIOeLgVrBkISkkLwpQ+aMi87vyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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