SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b883b486fcfe7524f9d617969b373cd8fd393849c137505ef20b3eed2afbcec7' 
  AND token = '9P5y/CtTnfGq6q0ZCTwvzaUpLP+9lwMGqQRj+ZWoc38=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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