SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b147ca6369e2c580cb29493840d4a21cba2a25a964a7058d7b19c103ba6736c' 
  AND token = 'r9peX8grSAtDYkvXdI2U/qOyiZftAbSPFjmXsALZjSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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