SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4256c0aa8edd0b24ca3cb3c25721d58be4aad753976caf2c2046ee4cc629ffcd' 
  AND token = 'llekD1Yv+TsLRlfspQKh4KqpzSV9gGFo+rOBsYYF+Kk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}