SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3851272ca4ce3185235d24e8ec4e23edffe7bc3f4136084db294a812208c272' 
  AND token = 'hV2EBPtfpUxAtgn/dOgJTARJIBrEyNLQb0PF5JwREqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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