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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '812c54ddd88dbd034e4fd35de51b5a0934359c81486d4ee8f56288eb35971e9a' 
  AND token = 'sJRG/3LurGjy2CiLMea5GJgTCydjY1phevrkmedItFo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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