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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b78876100ee47b2a6bc8face373fe5302a6532595e6a496fcd64a9bbff5c4cb' 
  AND token = 'URw3mVFfk7TFqcSorOgqdoB5KbXk9YSCjympV9abf14=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}