SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '235188d62cd2159bf03cd39deaf8f3754f58c59855cb7a8b8439818db2b3f02f' 
  AND token = '+JjDBFqvQOKXtVPRQ/gtRaHAk+5DfVMmnD2IcDkGEVA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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