SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf6c0d0996b97a10868afc6c41102268e24f6b797afd45dcc3f26193e6289465' 
  AND token = 'pOIZmBLe6xFrXFg29+zfVmyOCpWTIRPGG0/VHm2SJwk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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