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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '280f7e4433ed396ebebb1f5fd80eea90bb5fd8bd3a4c4c2f3e627fef298ee351' 
  AND token = '3oMnNsFGSr9PXTFj4Gy+I+btmJNIvPa9JnlSo9dqAU0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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