SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9df1947b06443cf509981419112a5c9902f40c30b1988e6535b73766dbad4d49' 
  AND token = 'ZqBFh+pkUtfFYBU5iLu4jy71fzMRmUWP5NQKM4gvecI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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