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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac3c5c1e1ef7fc6f6f499ce60a06539c9c33257f1ad3260ba7a1212fa6b61b3c' 
  AND token = 'rLXkyWu5ufgQAc/RgSlgr492XwqRZrWy//1SVxXdXZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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