SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e03ed209eeb6f73d2bed7109d4403a98fb409cabc0a64261d5a04b88842b7deb' 
  AND token = '2kMCpu7KpLKosnjIGtKMpSndRnLc9Fv3IkmxjZ2YSN0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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