SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '396b46f300b0c4e37259a7cdba1e8a2c5b39d85bc908e285f26655090f0f5ead' 
  AND token = 'oIQgm8/GRkFPtO8lFF2xyjjNquY8v0Nz8o+ETMXvTEQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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