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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '256ceb1828071e6704dd464e4dd2abb90bd4dbb68b20f0ca23b0f98ca21e1d8a' 
  AND token = 'YAVWzLzDVRQ+L+z9v2ArEGCnawhZweS2LFLg4eotvm0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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