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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5f8a85c867ce0716182aa900ddb9afdddc63df14a91ac38dcffc0c0ea3171d2' 
  AND token = 'S1dOBiI/3t2ZNkcHE3of5EtSvkZ3RTQmlgm/DUDHEg4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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