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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f1b6f0fe06a2b4ae4211ab234d5d920d81f30a8a000e84d93fbbc690ac59f1ec' 
  AND token = 'sb2eic+MoYuYNOP5geRYasS11iOoCjHHmm1IDKCw8Dk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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