SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '39d8158bbf7be109f4af1e5a4e1053f865254e7ec31af2489532c83588cba256' 
  AND token = '878k2z9U1hQ3ggqkyJmT3GD5Y/5Jn7dK7Zo+okuRgk4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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