SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90c918e6083a4ed283bbf52fdbd3252f921658f0d5b932d791376d5a00132b0a' 
  AND token = 'fmVsLNAwTPh2fFeYOWJhL6cGzOgLQ1Zr/VsIP1/7/rA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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