SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '250cc56353511c88a2bb8444bd5ae379b5102ec8a06c1d505b227c8744570b85' 
  AND token = 'kZ7Qml/nGIFn87MjlXyYK8HNmnKep1VSWR5qCRknDRc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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