SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '974f5a28999471ae9ef9352352f9b060496aecd82bde90934c84bbd4dad4259b' 
  AND token = 'flKkzD90aOkQLdGJYgl6dZ2REJSuJ0NY/csVufvwIu4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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