SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6797ba1533d7de945679c0b6737f58de703b85b8d8f239d334e20d7c69156750' 
  AND token = 'r+UQp2D6KqgdUwz+VmKE0jSeIkMpvfGz72CnL2D1Bnc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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