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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5d9246efcde2bde867f9b9e2291d2b7abc3c261a6c2e2b9ba8f4f3e7d68d823' 
  AND token = 'i/zJstn4Lh9Z/rptIGpvgSazg/e4BQiQiSCKwAeU87U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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