SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b878de5c3c49e6e28373b96e63f5a2622bb3376d3965d4449ac33817a9c5ce1f' 
  AND token = '+7d/1aGFxq3z/8AimiXq4+NxUl4gfJznM2GDCgriZHA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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