SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bc21e897726ede5b63898ee68d5ff97810eea37f1e597fca6ad7fd626e7702be' 
  AND token = 'LhMXkExeMdAu6rZxYfPyukuBbA/WPprAQPakBbQZ1r8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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