SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b8da8e0b53d14a8b160da7654c5368e901259e64edfcc0fe2ccb8288c08b03' 
  AND token = 'MIgv+HkQSl37xGymw/KQ1nqfdXPmrWtJF32YurahiLo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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