SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6ff1f5f5143bcad86bb45fd1e581e7056c8b6012a11a3f5387155004a78619b' 
  AND token = 'fg83XNHzg1waBv907gn1+Q6vAT/owgEXgdqYlt2KMFw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}