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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6dfe1c8afd5968c9cb2766db0b2711fab3c9e3bffb8628828fbb7e6bf1a3b5e' 
  AND token = 'xXggxi0R5uEiOos/OR6WqVOdoMFJiRtj4qxdhFoZ3qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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