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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b36b98acb132432401789ff35047422da87cf8c9f19608206ea8889027ea98df' 
  AND token = 'MpYuiHKfYrDtyBPAXMIemx8niRhPrhPsUnGrqTMmKBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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