SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0a76eb707168e918f5f0f2f7396cc11f8d36ddba512c17be1da85029a5dc8fa' 
  AND token = 'k7oxe6tLgn+XbLDIhitWvK16qFjBgtFq4idUUahvvJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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