SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'de3735c57c2fb867cfec35761c11a00536aa22a3525b375588a809e3866d5e85' 
  AND token = 'V52AR7tecFOqQm1h1QtVp9yhiEghUc9T49MsNFRn1j4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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