SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3660a34c65d5404213b556e6286918cdbb47f6a5b7e67c9f165095c643107523' 
  AND token = '6H6jg4lKDhtG4vdOmG1PMizTXIwwdvzv3NnrcXEQUlw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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