SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0bfe56b515ff462da027a844db1b365e3819f317a6ecb4038564738ce1cae4c' 
  AND token = 'VS9SvLmaD6hzEjr1FElkE8Flno8lH6xictKM1Cp19DY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}