SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b99c774c7becdda7e0aa59413da64bf773ca67a3e65af2a456ae578cc935401d' 
  AND token = 'bjiEE1ZfrZDKqZZkXAspr4ava919tmxblaQkBMygB90=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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