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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3a58bfe9dc3392247275dec5e1a4c7822afc0c4c868d08b46ec459cfa839999' 
  AND token = 'PKv4WdaIjHToXFjCUlFxx4MMVXZ8CAXM2gGEDrTDIKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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