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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b66c87171923e43d11b1580de35fd19b2c99ada107d8a978d6caefa9c08d1ba4' 
  AND token = 'y/GKioJ20GpeXzmRDTthg2GHtHJ+4kMDw3HdFWmMIuI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}