SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1976993b54457e15bef1276b629fd020c9575add0d0e917d764c47fab5027683' 
  AND token = 'jmTMxvD1EFUCgWUsFW4z2a77X3vfFUnsW9AQXkozuco=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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