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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fcf265a1ef4a1099bbb0ab4b7b0dc74e7efbb528d912943afdb43a2daf63a245' 
  AND token = 'OQ+tdQiOWB1vfOXkStVm1owm0Ud1Ji4qGUns7/Evkm0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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