SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55ce5292b1eebe22df6ea38f584674b724bf4b1ec8fedda848afcbe29db0504d' 
  AND token = '20URquXNk+qBzpDD2jSt+BktHitiSMdFuhGAmCzUz18=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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