SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fea7f83cc50c0a51e652b40fb2d375b762ffcaa3f2d9255d758bafb25be7cdac' 
  AND token = 'zvTOMEvCCdhWqXqDax9HBw5bJCQ/f6sUKEqwmwXwjbc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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