SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3b8670735bad507e2bdf204029beafa6f84f19d13ed31c8becd522047725b18' 
  AND token = 'eR42LW4eWFtRxglO1Kis/piisAp8/NmRRhZerRz8NXQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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