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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e2b855c92d379dcf07f9179a526c2c15da521ed2f7e6e4a3264ffa448d4dc5f5' 
  AND token = 'DoVQ9WOcRMCvsO+Bn2ePndO6aLDAb7+j7T+H9lvUPjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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