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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8be81c5ba20abf7e4220995ab3c9b59b8da66ad71dead81dd55a1a4084836bd' 
  AND token = 'vJfZVfQgGlbxYsGbMQxZuOn5HR+fAJEot07Rd8Q3Jp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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