SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '27214d312cf5f3a0653178699d31f6318a4ef89b11e3db999140d5cb75593636' 
  AND token = 'aHm+ShVTo0OczBXc3L2lpveCVV/ELTABA1tZgCEjsuo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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