SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e29ceff128c009374c3663e9b66285fc883964935ccc655e3bcb578c670e60e' 
  AND token = '0cvp3ixVn6Kz7gH8PMmpgi+OJWbeHsKLGeTgCgX3AXQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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