SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6cd87670a506beb73252780f8af2f474190a31d122d93fb74c4535ebc2dc2ae' 
  AND token = '4K6gdSLPTRhY3/PkQGSFv4uzvzz1wPRRNK+pLxzqNxE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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