SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '376cf848aa926eb68de3cb56af368fb9ab42415b7d789638ee630a5209e6b50c' 
  AND token = 'gnZYZdKrsyGWL9fj1qPOlkLQ/+msTn1cC3hRaTvXjww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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