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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8e6a509ce631236f91143743086b4364c0e64d6a23c250d5e2526f4aefc725b' 
  AND token = 'PBYg7+W8yGt2LLr93+In3m16REP44DWcmsrskiC3SNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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