SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878b2a947dc69da042b15673bf947d88a817f0acaef4f500ed0e3b544e580714' 
  AND token = 'UEJ3bxCcSIREROEOl1YwmuGWUV2Btf23LmV3iNm4K48=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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