SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f642bc345c719f659dcc58a06a9bc61b81d732ac3772900a45e8d316c91dcfe' 
  AND token = '7+QS5PzXSJbujceg9/hi1guqtI2n56PRSGwlffKPkZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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