SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a8c2b9e731435634ca5fb5e1e36cb35f762c2362171c7a320e545deaab7c26c' 
  AND token = 'vHCYVUojhFtWj5ntNkbnzD4VZ+lLPFgvny/q3Vn9CBc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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