SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '49f8a1ac8342ee03d409aecc73b0776c142d6755955eda3852b0fa0d32f1777e' 
  AND token = '7tlwMjkIr8pH/pnbqxWlZMKYSqH0Hv2cIVLsyFWVaBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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