SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b521d7f96608fbd947f6c951a67d292bdca7b62e754c1c44acac6c973775ddc' 
  AND token = 'NvRJKfswkdPGT6Jji/RZawUZ3qRtSgfhs51phSMv4ww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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