SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec506686b51b894dee8bb3fd282495896d565f190d26185bcf329a8675f735d3' 
  AND token = '+026xGROp/eprF/D/rlSWTNjiVrRZnILpA+0rYQwwCI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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