SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76af75cc3fb7f8474e87073d9b2649a9139eb0fcdfa75fa0a2d5ee9b27479f61' 
  AND token = 'z+9KV6Zr8mgUBMJpocdgjRGc6FIy6gZRwOcYfsd1E+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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