SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fff790225c6e1c275475c93040944d6015de84633c41ce307d15e49b3e087b8e' 
  AND token = '5DEMrzO5GJx7ixAnshGUQUgeDop9QTZYCgNcNPtEYWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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