SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fbc38520f35dd04894c60e6f3311ceff22f6f96bbafbe2b7a4dcfbe2e621c3d7' 
  AND token = 'MmKanK2sppMXmQ7wnOVleFpXpiRX/VKKdtOmHLEAUeg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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