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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f68b3ad736c7dc340a8586f7d597c9d40bca950be57c97312b957189acc0dc1' 
  AND token = 'JRiVnSaEjGdmDiYGizLk+0/uZ/PJ/kVPGXDGxQSgS54=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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