SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd97e91b454231e049afe7a87f47655fac441974ebfcc93b8d4684b7439139ace' 
  AND token = 'JQs5sAT698UrgzZ8ZULHhyZf/YPlUqw3vVt+K5lmQCc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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