SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d3759236a8957b9138d28dfa25e2e7771895e7a7f7b5835130a5fb51f58e88d' 
  AND token = 'bC+8Upx06xMtMHWTQU2UWlkMk9mHihDbP1OGzkyteug=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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