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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68ec402c7e918a498bde394af4965798bf1d875492dd2708e935a3e2c286956b' 
  AND token = 'uKJfC+ytNLHZEmCKO6SlumuJ2awQKP9om+IH4j2TxUQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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