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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b81a5f9c47d3f5b215881ba1c70d2ced9fbdfd1a9dd7e5dfadd5e436b96fa30c' 
  AND token = '6nqQeQPirjI0YwNJ+CL14e3UBH2a41hc7Ui9eXBEMeo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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