SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd51240c5cc4ed869ea2599f2a776f189015e4074f054a9eff6e80f6ed6e87fb8' 
  AND token = 'c1FYoZE+2EFmLnOciRvKXarm+QNnNcyjG/RkoRtrh+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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