SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1916e7ceece69950b19dfa47654c8ee82eafeafe00364bcb41e3f2d13f31a682' 
  AND token = 'i7tpHIXjGCZ/tWOd8zzzltC9AsZiJJPNUzmBMIBP0Fg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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