SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f9bab918c3a0ce30facb926a2d45530ac775998b1b0179651585f2bfb57bd9' 
  AND token = '4jmx3M2Vq1vhEmMRRBpoOAtUdv+CP+DoDYazUhbv2HA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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