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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e46714be1df9b95ef251675447d998da8d304dcee895e868039a6be4ddfa5435' 
  AND token = 'Xa4uZfbSnFKCw+TYb5LFTNisvhcFptmoTIrDOSsEAaI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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